Ultrastructure of Dormant and Germinating Conidia of Aspergillus ochraceus

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Abstract
Ultrastructural changes during germination of Aspergillus ochraceus conidia were studied. The following ontogenetic stags were observed: 1) dormant stages; 2) hydration and expansion; 3) aggregation; and 4) germ tube formation. The dormant spore possessd a dehydrated cytoplasm enclosed by a wall consisting of an inner, relatively electron-transport zone and an outer electron-opaque zone. This wall in turn was surrounded by an outer, wrinkled layer that contained the rodlet region. Spore expansion was accompanied by formation of a new inner wall layer continuous with the germ tube wall formed during germination. Overlapping in time with formation of the new wall development of a substance that formed a fibrillar sheath about the spore. The sheath was responsible for spore aggregation as germination progressed. Generally, a single germ tube emerged from each conidiuim and was surrounded by a fibrillar sheath continuous with the sheath surrounding the spore. Numerous vesicles were located at the tip of the germ tube.